1. Technical Field
The disclosure relates to an optical element and fabrication method thereof, and in particular relates to a biaxial retardation film and fabrication method thereof.
2. Description of the Related Art
Liquid crystal displays (LCDs) have found wide applications in electronics used in daily lives, for example monitors, laptops, digital cameras, projectors, mobile phones and so on. Retardation films or optical compensation films can be used to improve problems such as contrast ratio reduction, gray scale stability, gray scale inversion and color shift encountered in wide viewing angle liquid crystal displays.
Cholesteric or negative C optically anisotropic coatings can improve the viewing angle performance in vertical alignment liquid crystal displays (VA-LCD) because rod-like liquid crystal molecules in a VA-LCD cell are vertically aligned in the off state, and this is similar to that of positive C optically anisotropic coatings (which may achieve optical compensation due to their positive retardation values). However, for typical 4-micron thick VA-LCD cells, if the positive retardation value is too large, overcompensation may result. Thus, cholesteric or negative C optically anisotropic coatings are often used to provide negative retardation as to offset the positive retardation for obtaining an optimal dark state.